Date: Thu, 21 Aug 1997 11:15:07 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Victor <fesenko AT pacific DOT net DOT sg>
cc: djgpp AT delorie DOT com
Subject: Re: [Q] wrapping functions with linker
In-Reply-To: <5tg75j$sj3$1@newton.pacific.net.sg>
Message-ID: <Pine.SUN.3.91.970821105239.26170A-100000@is>
MIME-Version: 1.0
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On Thu, 21 Aug 1997, Victor wrote:

> General Protection Fault at eip=1af61; flags=3056
> eax=00000025 ebx=0000000e ecx=fffe6ad1 edx=0001cc85 esi=0001cc2b
> edi=00000123	ebp=00000123 esp=00003006 cs=a7 ds=af es=af fs=8f
> gs=bf ss=33 error=0000

Is this under CWSDPMI?  It seems like the traceback is from CWSDPMI, and 
the registers seem to indicate that the crash is inside the DPMI server, 
not your program (ss != ds).

Your `malloc' replacement is not general enough, so it seems (e.g., 
`free' does nothing etc.), which might not be good enough for the startup 
code which calls `malloc' quite a lot.

It seems to me that if you would to use `alloca', it would have been much
easier.  Since your allocations are all freed before a function exits,
`alloca' is the best solution.  And it won't have any adverse effects on
the library.  You only need to know how much stack you need at most, and
set _stklen to that value. 

> The reason I'm using such a weird malloc() replacement is that I'm
> doing a program which could be running for a long time (probably days)
> and when I check available DPMI memory, it's going down all the time.
> I understand that after calling free() memory is added to a free
> memory pool, but the DPMI memory is going low at an alarming rate and
> the memory in the pool gets fragmented too (and I don't have any
> control over the memory in the pool).

If the `alloca' solution isn't good enough, try the GNU malloc (it's under
GPL).  It is specifically tailored to such cases (it relocates large
buffers to prevent fragmentation and minimize calls to `sbrk').  One place
to look is on GNU ftp sites; if you have Emacs sources installed, look
there for the files gmalloc.c and ralloc.c.  Emacs uses `malloc' and
`free' a lot, and it is also supposed to run for days (on Unix systems).